Electric lampholders



Jan. 28, 1964 K. s. ADIE ELECTRIC LAMPHOLDERS 2 Sheets-Sheet 1 FiledJan. 15, 1962 United States Patent 3,119,646 ELECTRIC LAMPHOLDERSKenneth Scott Adie, One Oak, Dove House Lane, Solihull, England FiledJan. 15, 1962, Ser. No. 166,105 4 (llaims. (Cl. 33967) This inventionrelates to screw lampholders for screwcap electric lamps said holderseach comprising a socket provided with electric supply contacts and witha screwthread so that the socket can receive and retain a screwthreadedplug on the lamp, such a holder being hereinafter referred to as a screwlampholder of the kind specified.

It is one object of the present invention to provide a screw lampholderin which a screw-threaded plug of an electric lamp can be resilientlygripped both in a radially inward and axially inward direction so thatthe lamp cannot be pulled out of the lampholder and will not becomeloosened when vibrated.

It is a further object of the present invention to provide a screwlampholder which is capable of receiving screwthreaded plugs havingdifferent thread forms.

It is a still further object of the present invention to provide a screwlampholder which does not cause a screw-threaded plug to be made aliveuntil the plug is almost completely within the socket.

It is a yet further object of the present invention to provide a screwlampholder which is inexpensive to produce.

The invention will now be described with reference to the accompanyingdrawings in which:

FIGURE 1 is a perspective view of a screw lampholder,

FIGURE 2 is a top-side plan view of FIGURE 1,

FIGURE 3 is an underside plan view of FIGURE 1,

FIGURE 4 is a cross-sectional view similar to FIG- URE 3,

FIGURE 5 is a diagrammatic side elevation of the lampholder but onlyshowing the resilient bar-like members in full lines and in positionsoccupied when not deformed,

FIGURE 6 is a similar view to FIGURE 5 but showing the resilientbar-like members deformed as a result of a screw-threaded plug of a lampbeing located therein,

FIGURE 7 is a fragmentary cross-sectional view of the holder on anenlarged scale and showing the positions assumed by the resilientbar-like members when deformed as a result of the screw-threaded plug ofa lamp being located in the socket and,

FIGURE 8 is a sectional view of FIGURE 7 on the lines 38 thereof.

The screw lampholder comprises a body 10 which is made of porcelain ormay be made of any other suitable rigid electrically insulating ornon-conductive material and includes a flange 11 formed with gaps 12 toreceive fixing screws whereby the lampholder can be secured in arequired position.

The body of the lampholder also comprises a cylindrical socket 13 toreceive the single start screw-threaded plug 14 of an electric lamp 15and said socket is formed by an irnperforate cylindricalside wall 16 anda rear end wall 17 and said socket at its forward end is formed with aninternal chamfer 18 to facilitate insertion of the plug 14 of the lampinto the socket. The diameter of the internal cylindrical surface 19 ofthe socket is greater than the major diameter, i.e. the crest diameterof the screw-thread on the plug 14 of the lamp intended for use with theholder.

Disposed centrally within the socket and projecting from the rear endwall 17 is an electrical contact 20 ice adapted to co-operate with thenormally provided central contact 21 at the end of the plug 14 of thelamp and said central contact 20 is stationary but may be spring loadedso as normally to be urged axially of the socket towards the forwardopen end thereof.

Disposed at one side of the socket and thus olfset from the centrethereof is a further electrical contact 22 which is resilient and isadapted to co-operate with the normally provided contact of the lampformed by a metal screwcap of the plug 14 and the contact 22 extendsonly a short distance from the end wall 17 so as to be engaged by themetal screw-cap only during final axial movement of the plug of the lampinto the socket. The contacts 20 and 22 are connected respectively withterminals 23 and 24 at the rear of the flange 11 and adapted to receiveelectrical power supply wires.

Formed in the internal cylindrical surface 19 of the socket are two sets25 and 26 of openings said sets being spaced apart axially of the socketa distance equal to twice the pitch of the screw-thread on the plug 14of the lamp. Each set of openings comprises four slots 27 and one blindhole 28 and three of the said four slots 27 are of right-angularformation when the socket is viewed in end elevation, see FIGURE 7, andthese four slots are spaced apart substantially equi-angularly relativeto a central longitudinal axis of the socket. The blind hole 28 isdisposed substantially radially of the socket. The openings extend onlypartially through the thickness of the side wall 16 which, as previouslystated, is imperforate.

The length of the mouth of each slot 27 opening onto the internalcylindrical surface 19 of the side wall 16 and in a circumferentialdirection is equal approximately to of the circumference of saidinternal cylindrical surface and the thickness of each slot, i.e. in adirection axially of the socket is much narrower than this, it beingslightly larger than the diameter of wire to be used in the socket andhereinafter to be more particularly described. Thus as viewed in frontelevation the mouth of each slot is of rectangular elongated formation,see FIGURE 1.

Adjacent but spaced a small distance circumferen-tially from one slot isthe blind hole 28 hereinbefore referred to which is of circularcross-sectional shape and is slightly larger in diameter than thethickness of each slot 27.

The five openings in a set are positioned so as to define a helix havingthe same pitch as vthe screw-thread on the plug 14 of the lamp and theblind hole 23 land the closely adjacent slot 27 are disposed an axialdistance apart corresponding to the pitch of the screw-thread. Each slot27 as viewed in front elevation is inclined at the helix angleaforesaid.

The sets of openings 25 and 26 are adapted respectively to receive loops2? and Sil made of resilient metal wire. The wire is preferably made ofstainless steel and is circular in cross-section and the diameter of thewire is such as to enable said wire to have an easy push-fit engagementwith the sets of openings. By way of example the wire may be 0.048 inchin diameter and t e thickness of the slots may be 0.056 inch and thediameter of the blind hole 28 may be 0.62 inch.

The wire loops 29 and 30 are each of angular and of substantially squareformation when not deformed, see FIGURES 3 and 4 so as to provide threecorners 3 1 which are rounded and are spaced Iapart relative to acentral axis of the loop and at a position opposite the middle corner ofthe three corners, the two ends 32 and 3-3 of the wire are spaced apartto form a gap 34 to permit of expansion and contraction of the loop andthe end 32 is disposed substantially radially outwardly.

Each of the wire loops 29' and 30 are conveniently planar in theirundeformed condition and the distance across opposite corners of eachloop is approximately equal to or slightly less than the distancebetween radially outermost parts of a pair of opposed slots 27 and eachwire loop can beinserted and located in the socket by radiallycompressing the loop and engaging the one end 32 in the blind hole 28 sothat said end is positively anchored against axial movement in androtary movement around the socket and the other end in the closelyadjacent slot 27 and the three corners 31 of the loop are engaged withthe other three right-angular slots 27 in the appropriate set ofopenings and when the loop is permitted freely to expand said loop isretained in the socket by the openings.

Whilst the free ends 32 and 33 of a loop and the corners 31 thereof aredisposed within the openings in the socket, straight resilient bar-like,i.e., elongated, members 35 of the loop extending between the cornersare disposed in :a chord-like manner across the side wall 16 of thesocket and are spaced from the inner cylindrical surface 19 of thesocket and owing to the helical formation of the openings the fourchord-like bars 35 of the loop are constrained into a somewhat helicalformation corresponding to one convolution of a screw-thread the pitchof which is the same as that of the screw-thread on the plug 14 of theelectric lamp. Thus two sets of resilient bar-like members are providedat positions'axially spaced apart along the socket.

Prior to insertion of the screw-threaded plug 14 of the lamp into thesocket, when the chord-like bars 35 are thus substantially straight andin an undeformed condition, pairs of opposed chord-like bars are spacedapart a distance equal to or slightly less than the minor diameter,i.e., the root diameter of the screw-thread on the plug 14 of the lamp.

When the two loops 29 and 30 of resilient wire'are positioned in thesocket the bar-like members collectively provide two axially spacedapart screw-thread-like convolutions formed of resilient bar-likemembers, the effective diameters of which convolutions are equal 'to orslightly less than the minor diameter of the screw-thread on thescrew-threaded plug 14 of the lamp and it should be appreciated that thetwo convolu-tions are arranged so as to for-m part of a single starthelix.

By inserting the screw-threaded plug 14 of an electric lamp into thesocket 13 and at the same time rotating the lamp about the longitudinalaxis of the socket the screw-threaded plug makes screw engagement withthe chord-like resilient bar-like members of the two loops and screwsinto the socket until the central contact on ;the lamp 21 abuts thecentral contact in the socket and final tightening rotation of the lampis applied until substantial resistance to rotation is felt. Theengagement of the end 32 of a wire loop in the blind hole 28 anchors theloop against movement circumtferentially in the socket and eachresilient bar-like member is supported adjacent its ends at 36 by theslots 27 against movement both axially and radially outwardly of thesocket so that when the final tightening rotation of the lamp iseffected up to a stop provided by the contact 20 in the socket theresilient bar-like members 35 are deformed, between their ends, radiallyoutwardly of the socket against the surface 19 as shown in FIGURE 7 toexert radially inward resilient pressure on the screw- :threaded plug14.

It should be appreciated that the four resilient bar-like members 35 ineach loop provide four-point contact with the plug 14 at positionsspaced 90 apart and thus said bar-like members are collectively disposedaround a major circumferential part, i.e., more than 180, of the sidewall whereby the plug is positioned centrally in the socket.

Whilst four resilient bar-like members 35 are provided in each loop itwill be appreciated that three or more resilient bar-like members may beemployed provided they are collectively disposed around a majorcircumferential part of the side wall so as to position the plugcentrally in the socket.

As a consequence of each resilient bar-like member 35 being deformedradially outwardly of the socket against the surface 19, each member,between its ends is caused by continued tightening rotation of the lampto be deformed axially outwardly of the socket as shown in FIGURE 8whereby said bar-like members exert axially inward resilient pressure onthe plug. Thus the plug is effectively locked centrally in the socket ina. manner preventing accidental unlocking, by for example, vibration andalternate heating and cooling of the members.

As considered from another aspect the screw-thread in the socket isformed of one or more rings, as hereinbefore defined, of triangular orother polygonal form made of resilient wire or rod with their sidesforming resilient bar-like members 35 extending as chords relative tothe internal cylindrical surface of the side wall 16 of the socket andsupported therefrom at their ends. As shown in FIGURE 3 in the rings ofpolygonal form the successive sides formed by the members 35 are gappedbetween their ends.

If desired the offset contact 22 may be omitted and the inner loop 30may be connected to the terminal 24 so that said inner loop 30 forms theoffset contact in the socket.

Whichever of the two forms the offset contact of the lampholder maytake, for cooperation with the screwthreaded plug of the lamp, .thisoffset lampholder contact is positioned adjacent the inner end of thesocket so that the plug only connects with said offset contact when theplug is entirely or substantially within the socket to such an extentthat the plug of the lamp is then inaccessible to a person inserting thelamp into the socket so that it is impossible for that person to receivean electric shock from the screw-threaded plug.

As it is virtually impossible for a person inserting a lamp into thelampholder to receive an electric shock there is no need for the openend of the socket to be provided with an outwardly flared skirt such asis normally provided and as the provision of a skirt tends to 'cause'thesocket to become overheated due to collection of the uprising current ofheated air from the lamp, the lampholders'according to the inventionremain relatively cool.

The lampholders according to the present invention provide the furtheradvantage that the resilient bar-like membersformingthe screw-thread ina single lampholder are readily self-adaptable to the different threadforms employed, for example, by British, American and Continental orother manufacturers of screw-cap electric lamps so that the differentscrew-threaded plugs, but in which the screw threads have the same pitchand lead, can each be inserted in an efiicient manner in the singlelampholder according to the present invention.

The diameter of the internal cylindrical surface 19 of the socket andthe cross-sectional diameter of the resilient bar-like members 35 aresuch that if said members are deformed radially outwardly so as to abutthe internal cylindrical'surface 19 the effective minor diameter of thedeformed members is such as to provide an interference fit with themajor diameter part of the screw-threaded plug of the lamp which theholder isintended to receive so as to prevent withdrawal of thescrew-threaded plug from the socket unless the said plug is screwed outof the socket. In other words the cross-sectional Size of the socket isless than the sum of the major diameter of the screw-threaded plugintended for the socket and twice the cross-sectional thickness of thewire of which the resilient bar-like members are made.

Whilst the lampholder illustrated in the drawings is provided with twosets of resilient bar-like members at positions axially spaced apartalong the socket only one set may be provided which is preferablydisposed adjacent the open end of the socket and the inner end of thesocket may be provided with location means adapted to bear on the sideof the screw-threaded plug of the lamp when the plug is inserted fullyinto the socket so as to locate and centralise the end of the plug atthe inner end of the socket.

The invention thus provides an electric screw lamp holder in which thelamp is held so as to be co-axial therewith and in a manner such thatthe lamp will not accidentally become loosened when tightened in thelampholder and furthermore said lampholder is less expensive to producethan known lampholders and a single lampholder is capable of receivingscrew-threaded plugs having different thread forms.

What I claim then is:

1. A screw lampholder comprising a socket made of electricallyinsulating rigid material to receive a screwthreaded plug of a screw capelectric lamp and Ihaving a rear end wall to close one end of thesocket, electrical contacts within the socket, including a centralelectrical abutment contact at the inner closed end of the socketagainst which a central electrical contact of the plug can abut, atleast one ring of polygonal form disposed in the socket to provide thesole screw-thread therein to receive the screw-threaded plug and thering being made of resilient wire and affording resilient bar-likemembers each normally extending as chords relative to an internalsurface of a sidewall of the socket and said members being supported bythe side wall at their ends against rotary and axial movement in thesocket whilst being normally free between their ends to move radiallyand axially, the cross-sectional size of the socket being less than thesum of the major diameter of the screw-threaded plug intended for thesocket and twice the crosscectional thickness of the wire so that afterthe screw-threaded plug of the lamp has been screwed into the screwthread afforded by the ring up to the central electrical abutmentcontact in the socket further rotation of the plug firstly deforms thebar-like members of the ring radially outwardly against said internalsurface of the side wall and secondly then deforms said members axiallyto cause said members to exert both radial and axial resilient grippingpressure on the plug and prevent its withdrawal from the socket unlesssaid plug is screwed out of the socket.

2. A screw lampholder according to claim 1 in which the electricalcontacts are provided adjacent the inner closed end of the socket so asto be capable of co-operating with the screw-threaded plug of the lamponly during the final axial movement of the plug into the socket so thatthe normally provided metal screw cap in which the screw is formed isnot rendered alive until the plug is almost completely within thesocket.

3. A screw lampholder comprising a socket made of electricallyinsulating rigid material to receive a screwthreaded plug of a screw capelectric lamp and having a rear end wall to close one end of the socket,the internal surface of an imperforate side wall of the socket beingformed with a plurality of openings which extend only partially throughthe side wall, electrical contacts within the socket, including acentral electrical abutment contact at the inner closed end of thesocket against which a central electrical contact of the plug can abut,at least one ring of polygonal form disposed in the socket to providethe sole screw-thread therein to receive the screwthreaded plug and thering being made of a loop of resilient metal wire affording a ring of atleast three resilient barlike members of which adjacent members togetherdefine corners which enter the openings in the side wall of the socketso that said members normally extend as chords relative to the internalsurface of the side wall and are supported by the side Wall at theirends against rotary and axial movement in the socket whilst beingnormally free between their ends to move radially and axially, thecross-sectional size of the socket being less than the sum of the majordiameter of the screw-threaded plug intended for the socket and twicethe cross-sectional thickness of the wire so that after thescrew-threaded plug of the lamp has been screwed into the screw-threadafforded by the ring up to the central electrical abutment contact inthe socket further rotation of the plug firstly deforms the bar-likemembers of the ring radially outwardly against said internal surface ofthe side wall and secondly then deforms said members axially to causesaid members to exert both radial and axial resilient gripping pressureon the plug and prevent its withdrawal from the socket unless said plugis screwed out of the socket.

4. A screw lampholder according to claim 3 in which the loop ofresilient metal wire affords ends which are spaced apartcircumferentially of the loop to provide a gap between said ends and oneend of the loop is directed substantially radially outwardly and entersa radially disposed opening in the internal surface of the side wall ofthe socket to support said one end positively against rotary and axialmovement in the socket and the other end of the loop enters an openingin said internal surface whereby said other end is supported againstaxial movement in the socket whilst permitting its rotary movement inthe socket to allow for expansion and contraction of the loop.

References Cited in the file of this patent UNITED STATES PATENTS1,167,473 Benjamin Jan. 11, 1916 1,238,849 Wacker Sept. 4, 19171,780,826 Kuhn Nov. 4, 1930 1,881,663 Kennedy Oct. 11, 1932 2,476,071Spiro July 12, 1949 2,668,278 Avery Feb. 2, 1954 2,874,741 Brancato Feb.24, 1959 FOREIGN PATENTS 137,562 Australia Jan. 8, 1950 658,761 FranceJan. 278, 1929 912,009 France Apr. 8, 1946 981,399 France Jan. 10, 1951997,233 France Sept. 12, 1951 1,171,784 France Oct. 6, 1958 1,036,971Germany Aug. 21, 1958 589,357 Great Britain June 18, 1947

1. A SCREW LAMPHOLDER COMPRISING A SOCKET MADE OF ELECTRICALLYINSULATING RIGID MATERIAL TO RECEIVE A SCREWTHREADED PLUG OF A SCREW CAPELECTRIC LAMP AND HAVING A REAR END WALL TO CLOSE ONE END OF THE SOCKET,ELECTRICAL CONTACTS WITHIN THE SOCKET, INCLUDING A CENTRAL ELECTRICALABUTMENT CONTACT AT THE INNER CLOSED END OF THE SOCKET AGAINST WHICH ACENTRAL ELECTRICAL CONTACT OF THE PLUG CAN ABUT, AT LEAST ONE RING OFPOLYGONAL FORM DISPOSED IN THE SOCKET TO PROVIDE THE SOLE SCREW-THREADTHEREIN TO RECEIVE THE SCREW-THREADED PLUG AND THE RING BEING MADE OFRESILIENT WIRE AND AFFORDING RESILIENT BAR-LIKE MEMBERS EACH NORMALLYEXTENDING AS CHORDS RELATIVE TO AN INTERNAL SURFACE OF A SIDEWALL OF THESOCKET AND SAID MEMBERS BEING SUPPORTED BY THE SIDE WALL AT THEIR ENDSAGAINST ROTARY AND AXIAL MOVEMENT IN THE SOCKET WHILST BEING NORMALLYFREE BETWEEN THEIR ENDS TO MOVE RADIALLY AND AXIALLY, THECROSS-SECTIONAL SIZE OF THE SOCKET BEING LESS THAN THE SUM OF THE MAJORDIAMETER OF THE SCREW-THREADED PLUG INTENDED FOR THE SOCKET AND TWICETHE CROSS-SECTIONAL THICKNESS OF THE WIRE SO THAT AFTER THESCREW-THREADED PLUG OF THE LAMP HAS BEEN SCREWED INTO THE SCREW THREADAFFORDED BY THE RING UP TO THE CENTRAL ELECTRICAL ABUTMENT CONTACT INTHE SOCKET FURTHER ROTATION OF THE PLUG FIRSTLY DEFORMS THE BAR-LIKEMEMBERS OF THE RING RADIALLY OUTWARDLY AGAINST SAID INTERNAL SURFACE OFTHE SIDE WALL AND SECONDLY THEN DEFORMS SAID MEMBERS AXIALLY TO CAUSESAID MEMBERS TO EXERT BOTH RADIAL AND AXIAL RESILIENT GRIPPING PRESSUREON THE PLUG AND PREVENT ITS WITHDRAWAL FROM THE SOCKET UNLESS SAID PLUGIS SCREWED OUT OF THE SOCKET.